My goal is to correlate specific subsets of nerve cell types with specific behavioral responses. The nervous system in hydra consists of a diffuse network of single nerve cells distributed unevenly throughout the body column. Several types of nerve cells have been identified but their function has not been determined. Many behavioral responses exist in hydra and, or these, the feeding behavior is particularly well documented. This behavior consists of a set of tentacle and hypostomal movements which result in prey capture and injestion. All nerve cells in hydra can be eliminated experimentally and the viability and developmental normalcy of these nerve-free animals is well documented. Nerve-free hydra exhibit no behavioral responses. When grafted together with normal hydra, nerve-free animals gradually regain normal nerve cell numbers and normal behavioral responses. Repopulation of nerve-free hydra has been used extensively as a technique to study the developmental roles of nerve cells. The functional roles of the nerve cells will be studied for the first time. This is possible since the recovery of behavioral responses involved in feeding occurs in a gradual, sequential, highly predictable fashion. The gradual recovery of specific behavioral responses accompanies the gradual recovery of nerve cells. To determine if specific subsets of nerve cells are associated with specific behavioral responses, newly developed monoclonal antibody staining techniques will be employed during the repopulation procedure. The appearance of different subsets of nerves, their density, and their location will be correlated with the sequential reappearance of specific feeding responses.